Dosing pump system

ABSTRACT

A compact, modular dosing pump system that is capable of microdose and macrodose volume flow rates, reduces or eliminates the need for additional flow control components such as temperature and pressure sensors, and utilizes a wider operational flow range than existing systems while maintaining the level of accuracy and precision exhibited by conventional dosing pump systems is provided. The dosing pump utilizes a a control system to deliver a range of fluid volumes. The control system monitors the motor emf voltage, calculates the flow rate, and makes adjustments to the pump motor voltage to precisely maintain the desired flowrate.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of, and claims priority toU.S. patent application Ser. No. 16/108,148 filed Aug. 22, 2018 which isa divisional application of, and claims priority to U.S. patentapplication Ser. No. 14/959,019 filed Dec. 4, 2015 which is a divisionalapplication of and claims priority to U.S. patent application Ser. No.13/589,932 filed Aug. 20, 2012 which claims priority to U.S. ProvisionalApplication Ser. No. 61/542,628 filed Oct. 3, 2011, the entirety of allof which are incorporated herein by this reference.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

BACKGROUND OF THE INVENTION

The present invention generally relates to devices capable of deliveringprecisely metered fluid volumes. Specifically, the invention includes apump that may provide both a microdose and macrodose so as to accuratelydeliver a precise volume of fluid with high resolution adjustment over awide range of microdose and macrodose volumes. The invention can beconfigured for use in fields which include medical, pharmaceutical, foodand beverage, industrial process, laboratory, and chemical, as well ascommercial and consumer applications.

Precise dosing pump systems are complex and expensive systems, arehighly specialized, and are limited to particular applications. Thehighly specialized nature of dosing pumps systems limits theirperformance capabilities to a narrow range of operation. Furthermore,due to their high cost, dosing pump systems are typically limited tohigh-end applications in fields such as medical and industrial, whilecommercial and consumer applications have limited access to thetechnology.

Generally, dosing pumps are electrically powered devices, and may beoperated utilizing several technologies such as solenoids, gears, adiaphragm and peristaltic actuation. Regardless of the pump technology,however, dosing pumps are typically designed for and limited toproviding very low flow rates such as 0.01 millileters per minute to 5milliliters per minute. In these prior systems, the low flow rate isnecessary in order to precisely control the output of the fluid. Thedrawback to the low flow rate, however, is that dosing pump systems havea limited range of adjustability such that they are not effective tooperate outside of the nominal design flow rate. Use of a higher flowrate dosing pump, such as a pump that operates in a range of 20milliliters per minute to 50 milliliters per minute, in order to expandthe range of flow rates is typically not an option because the increasedflow rate comes at the loss of accuracy and precision. Therefore, dosingpumps capable of precisely controlling macrodose flow are expensive andhighly uncommon.

Both precise microdose pumps as well as macrodose pumps tend to beexpensive. Also increasing the cost is the need of certain applicationsthat require both microdosing and macrodosing because more than one pumpis required to achieve all of the desired dosing ranges. Current dosingpumps lack the necessary degree of adjustability to cover large rangesof flow rate.

Further drawbacks of prior dosing pump systems are the variety ofdevices in addition to the pump that are required in order to monitorand control the flow of fluid. Flow meters, adjustable flow controls,pressure sensors, and temperature sensors are all needed in order fordosing pump systems to achieve their precision and monitor flow. Theseadditional components contribute to the complexity and cost of thesystem, as well as add physical bulk.

The sensitivity of readily available flow sensors, such as turbinesensors, is also not sufficient for accurately determining the flow rateof fluids at microdosing levels, generally within the range of 0.01millileters per minute to 5 milliliters per minute. In the case oftraditional turbine sensor, the microdose flow rate cannot adequatelyspin the turbine to generate sufficient signal to determine the actualflow rate of the fluid. Thus, In a traditional microdosing system, suchflow sensors cannot be utilized because the pump operates to draw in andexpel fluid at essentially the same microdosing rate resulting in aninput flow and an output flow that are each at microdosing levels. Insuch systems, a specialized microdosing sensor must be utilized.Microdosing sensors have significant drawbacks such as a high cost,generally thousands of dollars. Additionally, they are often applicationspecific and must be specially designed.

The selection of these components is typically based on achieving anominal microdose or macrodose flow rate fluid to enable a specificdosing pump to expel fluids of a particular, narrow viscosity range. Thedesign of the particular dosing system is thus limited to a particularflow rate for a particular fluid viscosity. If a change to the nominalflow rate is desired, or the viscosity of the fluid changes, the dosingpump must be re-engineered, or replaced altogether, along othercomponents of the dosing pump system (flow controls, etc.) in order tomaintain the precision of the system.

In summary, existing dosing pump systems can be configured to provideaccurate, high-precision fluid delivery. However, this is achievableonly within a narrow operational range and through the assembly of acomplex and expensive flow control system.

SUMMARY OF THE INVENTION

The present invention provides a compact, preferably modular dosing pumpsystem that is capable of microdose and macrodose volume flow rates,reduces or eliminates the need for additional flow control componentssuch as temperature and pressure sensors, and flow meters, and utilizesa wider operational flow range than existing systems while maintainingthe level of accuracy and precision exhibited by conventional dosingpump systems. In the preferred embodiment, the dosing pump utilizes apump and flow circuit to deliver a range of fluid volumes. The flowcircuit utilizes a networked system of fluid paths, orifices, and valvesto route fluid through the dosing pump system in response to a pressuredifferential between fluid inlet and fluid outlet ports. Furtherembodiments of the invention include a flow circuit with one or moreorifice size selectors and a flow circuit with a secondary, adjustableoutlet flow orifice, and yet another embodiment of the inventionincludes a closed loop control system to monitor and control the dosingpump flow rate.

By utilizing the flow control circuit, the dosing pump achieves a levelof precise flow control even when a standard, non-dosing rated fluidpump is used within the system. That is, pumps having wide variances inprecision tolerance may be utilized in conjunction with the flow circuitand the dosing pump system will still achieve the narrow precisiontolerance desired. This results in a number of advantages. For example,the range of adjustability of the flow rate is substantially greaterthan existing dosing systems. Also, the dosing pump system has thecapability to precisely control microdose flow rates as well asmacrodose flow rates. Furthermore, because a dosing rated fluid pump isnot required, the cost of the fluid pump may be substantially reduced.

The dosing pump system described herein may be further enhanced by acontrol system. In order to control the operation of the dosing pumpsystem, the controller, which is preferably a microprocessor basedcontroller, monitors the operation of the pump motor. In so doing, thecontroller monitors the flow rate of the system and may make necessaryadjustments to the pump's operation in order to adjust the flow rate ofthe dosing pump system. The controller may further monitor and controlother operations of the dosing pump system such as total volumeexpelled. By utilizing the controller to monitor the pump operation,additional sensors such as pressure sensors, temperature sensors, andflow meters are not necessary and the overall bulk and cost of thedosing pump system may be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of an embodiment of the dosing pump system.

FIG. 2 is a schematic of an embodiment of the flow circuit.

FIG. 3 is a sectional view of the orifice selector.

FIG. 4 is a schematic of the control system.

FIG. 5 is a sectional view of an alternate embodiment of the dosing pumpsystem.

FIG. 6 is a schematic of an alternate embodiment of the flow circuit.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The preferred embodiments of the present invention are described withreference to the drawings below. In the drawings, like numbers are usedto refer to like elements. The construction of the dosing pump iscomprised of two primary subsystems: a fluid pump and a flow circuit. Acontroller, which may be, and preferably is, a microprocessor basedcontrol system, may also be utilized to provide closed loop feedbackcontrol of the dosing pump system. The pump, flow circuit, and controlsystem are assembled into a compact, modular dosing pump system. Thedosing pump system includes a fluid inlet port to couple to a fluidsource and a fluid outlet port to discharge the fluid; no flow controldevices are required external to the dosing pump system.

Referring to FIG. 1, the fluid pump 1 is assembled to, and in fluidcommunication with, the flow circuit, generally identified as 2. Thefluid pump 1 provides a pressure differential to move fluid through thesystem. The flow circuit 2 routes fluid in though a circuit fluid inletport 3, through a network of flow passages of the flow circuit 2, anddischarges fluid at a circuit fluid outlet port 4. The flow circuit 2contains internal flow control features too, which may control the flowcharacteristics of the system.

Referring to FIG. 1 and FIG. 2, the two main features of the flowcircuit 2 may be seen. The first is the flow bypass loop where fluidflow enters from inlet port 3 into an input flow channel 5 and thenflows to the pump input 6 of fluid pump 1. The fluid then travels out offluid pump 1 through pump output 7 and into output flow channel 8. Thefluid then reaches a junction 9 in the flow circuit 2 at which pointsome of the fluid is diverted along an outlet branch flow channel 10while the remaining fluid continues through output flow channel 8 toflow orifice 11 a and through a bypass loop valve 12 a. After passingthrough bypass loop valve 12 a, the fluid flows through return channel13 and is routed back to junction point 14 where it joins incoming fluidand is routed back through flow circuit 2.

As stated above, some of the fluid is diverted at junction 9. Thediverted fluid flows from junction 9 along outlet branch flow channel 10and then through a flow orifice 11 b. The fluid then flows through anoutlet branch valve 12 b through exhaust channel 15 and out of thesystem through outlet port 4. As shown in FIG. 1, the junction 9,orifice 11 a and bypass loop valve 12 a connecting with junction point14 creates a bypass loop in the flow circuit, while the junction 9,orifice 11 b and outlet branch channel valve 12 b create an outputbranch. It should be appreciated that the various flow channelsinterconnecting the components in the flow circuit may be of a varietyof lengths. The flow channels are provided for explanatory purposes anddepending on the desired configuration of the pump may be constructed asan indistinguishable part of another element. For example, the exhaustchannel 15 could be shortened such that the outlet port 4 and theexhaust channel were one in the same. A relatively large flow ratedevelops within the bypass loop, while a lower flow rate developsthrough the outlet flow branch. The lower flow rate developed throughthe outlet flow branch is predictable and proportional to the flow ratethough the bypass loop.

While orifice 11 a and a bypass loop valve 12 a are located within thebypass loop, outlet branch flow channel 10, orifice 11 b and an outletbranch valve 12 b are located within an outlet branch of the flowcircuit 2. The sizes of the two flow orifices 11 a and 11 b determinethe flow characteristics of the system, and they are sized according tothe desired flow rate and the particular fluid properties of theapplication (e.g. the fluid viscosity). With respective flow orificesize selection, the flow circuit can precisely control a wide range offlow rates; from microdose flow rates up to macrodose flow rates. Thebypass loop valve 12 a within the bypass loop acts as an integral flowcontrol device; its cracking pressure provides flow resistance and inturn creates a rise in pressure within the bypass loop. This contributesto flow rate proportioning between the outlet flow branch and the bypassloop.

The sizes of flow orifices 11 a and 11 b are selected based upon theproperties of the fluid, primarily viscosity, and the intended flow raterange of a particular application. Once the orifice size selections havebeen made, the output flow from the dosing pump is precisely adjustableby means of varying the pump motor voltage. As the applied pump motorvoltage is increased or decreased, the bypass loop maintainsproportional flow between itself and the outlet flow branch, and theresulting outlet flow from the dosing pump increases or decreaseslinearly with respect the applied motor voltage. The linear responsebetween pump motor voltage and dosing pump flow rate providespredictable, high resolution adjustment of the dosing pump output.

The linear relationship between the voltage applied to the pump motorand the subsequent dosing pump output flow rate is advantageous ininstances where a dosing pump configured for a particular fluidviscosity and flow rate is used in different equipment configurations.For example, the dosing pump may be configured for a common fluidcomponent used in a variety of equipment configurations. The differentequipment configurations may locate the dosing pump at different flowdistances from the dispensing point, and/or the equipment may havedifferences in their respective dispensing point; these are only twoexamples of dissimilar physical conditions between equipmentconfigurations that are external to the dosing pump and that may impactthe resultant fluid flow rate through the system. The dosing pump,however, can have its outlet flow rate predictably adjusted by means ofpump motor voltage adjustment to yield the same system flow rate in thedifferent equipment configurations.

Preferably, the bypass loop valve 12 a and the outlet branch valve 12 bare check valves. The flow resistance created by bypass loop valve 12 aalso allows the dosing pump to self prime. Both valves 12 a and 12 bfunction as back flow prevention devices. Preferably the crackingpressure of bypass loop valve 12 a is greater than that of outlet branchvalve 12 b. In such a configuration, the higher cracking pressure ofbypass loop valve 12 a ensures that fluid is properly diverted atjunction point 9, causing fluid flow through outlet branch valve 112 b.

FIG. 3 pertains to an alternate embodiment of the present invention.Shown in FIG. 3 is a cross section of a flow circuit 2 including anorifice size selector 30. Additional orifice size selectors could alsobe included. The orifice size selector 30 further includes a pluralityof flow orifices 30 a, 30 b, 30 c, 30 d, 30 e and 30 f arranged in anarray. In the particular embodiment of FIG. 3, the orifice size selectormay be rotated as indicated by arrows 31 so as to align one of the floworifices into with flow path 32. The orifice size selector 30 may beincluded for either the bypass loop orifice or outlet flow branchorifice, or both. Preferably, the orifice size selector 29 may be placedat the inlet of bypass loop valve 12 a, the inlet of outlet branch valve12 b or both. Essentially, it is preferred that the orifice sizeselector replace either of orifice 11 a, orifice 11 b, or both.

The inclusion of the orifice size selector 30 provides for a single flowcircuit capable of several flow rate settings and compatible withseveral different fluid types. In the embodiment of FIG. 3, each settingis achieved by rotating the orifice selector to the appropriate orificesize for the particular setting. For example, the fluid circuit 2including an orifice size selector 30 may be utilized in a dosing pumpapplication where the dosing pump must pump different fluids, each withsubstantially different fluid properties. In use, the orifice sizeselector 30 is rotated so that the appropriate flow orifice is utilizedfor each fluid pumped through the system. Alternately, where a singledosing pump must accurately provide a microdose flow rate in someinstances and a macrodose flow rate in others, the orifice size selectormay be utilized to select the proper orifice sizes to supply the properflow rates for both instances.

While the particular orifice selector depicted in FIG. 3 issubstantially circular, having orifices arranged around itscircumference, it should be appreciated that different sized and shapedorifice selectors could be utilized, such as a linear orifice selectorthat is reciprocated in order to select a proper orifice

As presented in FIG. 1, the flow circuit may be constructed from anassembly of manifold bodies with internal flow paths; the manifoldbodies being manufactured by, but not limited to, machined, cast,injection molded, or some combination thereof. Another embodiment ofinvention is a flow circuit with flow paths constructed from flexible orrigid tubing, or some combination thereof. Yet another embodiment of theinvention is a flow circuit constructed from a combination of manifoldbodies with internal flow paths and flexible or rigid tubing.

The fluid pump is not limited to a particular type of pump technology,and pumps such as diaphragm, gear, solenoid, rotary vane, flexibleimpeller, or other type of pump suitable for a particular applicationmay be used.

One embodiment of the present invention utilizes a closed loop controlsystem in combination with the dosing pump system described above. FIG.4 is a depiction of a control system 40 for use in combination with adosing pump system. As shown, the controller is preferably amicroprocessor based controller 41. The control system includes allfunctions necessary to operate the dosing pump system. The controlsystem controls the power output to the pump motor (not shown),preferably through pulse width modulation (PWM) of the pump motorvoltage 42, while monitoring the electrical behavior of the motor,specifically the motor Electromotive Force (emf) voltage 43, to provideclosed loop flow control of the fluid flow. The motor emf voltage isproportional to the real-time discharge flow rate. By monitoring themotor emf voltage 43, the control system 41 calculates the flow rate andmakes adjustments to the pump motor voltage 42 to precisely maintain thedesired flow rate. Typically, dosing pump systems require flow ratesensors (such as paddle wheel or turbine type flow meters) to determinethe fluid flow rate. By utilizing the pump motor emf 43, the presentinvention may determine flow rate without requiring the use of suchadditional flow sensors. Additionally, the control system 41 can use theflow rate information to calculate the total fluid volume that has beenpumped.

Another advantage of sensing the motor emf voltage 43 is that thecontrol system 41 can detect when the fluid supply to the pump hasdepleted. Typically, an additional device such as a pressure switch isrequired to detect when a supply of fluid has been depleted. Bymonitoring the changes in the emf voltage, the present invention candetect the depletion of the supply without any additional devices.

Preferably, the control system may included a normalization functionwhich compensates for physical differences between individual pumps toensure that the dosing pump's output flow rate is not affected by thephysical differences of the motors. For instance, a particular pumpmodel's motor windings may have minor physical differences between eachmotor which may result a variation in the emf voltage that the controlsystem measures. The normalization function compares an input value,such as the actual emf voltage response, to a predetermined value, suchas a predefined reference response, to determine an output value, suchas an value corresponding to the appropriate pulse width modulationsignal necessary to properly adjust the operation of the fluid pump, andthe control system utilizes the output value to make the appropriateadjustments to correct for the variation. Thus, the control systemthrough the utilization of the normalization function can correct for awide range of different fluid types, flow rates, viscosities, etc,

The control system may additionally feature inputs and outputs which cancommunicate with an external control system 50 of one or more devices,such as a computer or other controller. This communication may provideflow rate 44, total volume 45, and fluid supply information (such as afluid supply empty signal) 46, as well as additional information 47about the operation of the dosing pump. This allows the external deviceto alternately control the pump in several different fashions such as:turning the pump on or off; sending signals defining the flow rate thepump should run at; and sending signals of how much total fluid volumeshould be pumped. Another example is the control system receiving apredefined formula 48 from an external control device, the formula 48containing information about one or more particular fluids. Thisinformation may include the volume of fluid to be pumped, the flow rate,as well as fluid property variables for correct emf vs. flow ratecalculations. Furthermore, the control system may receive additionalinput signals 49 from an external control device, to serve a multitudeof purposes; some examples include receipt of microprocessor firmwareupdates and test mode commands.

In turn, the control system may output information back to the externalcontrol device such as flow rate 44, total volume pumped 45, and fluidsupply information (such as a fluid supply empty signal) 46. Forexample, a supply depletion signal may be sent from the control systemto alert the external control device that the supply fluid has beendepleted, allowing the external control device to take further actions.While the controller of the control system may receive and send inputand output signals to an external control device 50, it is alsocontemplated that the control system may receive manual inputs directlyfrom an input device 51, such as a keyboard, dial, mouse, or touchscreen, and send outputs directly to an output device such as a displayscreen (not shown).

It is contemplated that the controller may be provided with a variety ofpredefined values which may be utilized by the controller, particularlyin response to an input value, in order to control the operation of thepump system. For example, the controller may be provided with a set ofoutput flow rate values. The output flow rate values may correspond tothe desired flow rates for particular products to be pumped. Thecontroller may receive an input, either from another controller, amanual input, or a sensor input, identifying the fluid to be pumped as aparticular product or as having a particular characteristic. Inresponse, the controller identifies the appropriate predefined outputflow rate corresponding to the product information input and controlsthe operation of the pump system, such as adjusting the power to thepump or adjusting one or more orifice size selectors, such that theappropriate output flow rate is achieved.

The control system may also be configured to operate within a network ofother controllers. Accordingly, a dosing pump such as that describedabove with respect to FIG. 1, may be configured to operate inconjunction with a control system, also as described above. A pluralityof dosing pumps, so configured may be connected together into a networkof controllable dosing pumps. Preferably, the controller, or controlsystem, of each dosing pump in the network may be preprogrammed with adefined set of flow rates, each flow rate being assigned to a networkaddress identification for a particular controller. The controller maybe manually or automatically assigned a network address identificationby means of physical electrical connection, software programming, orother known method. Once the network identifications have been assigned,each controller will then automatically drive the respective dosing pumpto dispense the preprogrammed target flow rate for the respectivenetwork address whenever a “dispense” command is received by thecontroller. The dispense command may be received from an externalcontrol system or from a direct input to the controller.

The control system provides a high degree of precision that allows thedosing pump to operate within desired tolerances over a wide range ofdoses. The operation of the pump can be adjusted to increase fluid flowcapacity by forcing a high volume of fluid through the system. Forexample, one embodiment of the present invention operates in a range ofapproximately 0.1 milliliters per minute up to approximately 600milliliters per minute, the structure and control system being capableof adjusting the flow rate throughout the entire range.

The self contained nature of the preferred embodiment allows the dosingpump to be used either as a stand-alone component, or as modular devicewithin a larger system. Requiring no external flow control devices orsensors allows the preferred embodiment to be easily adapted to a widerange of applications. For example, the dosing pump may be usedstand-alone to manually add a dose of a chemical compound within anexperimental laboratory application. Another example may be theinvention used as one of a plurality of dosing pumps within an automatedfood processing device, with the invention's control system receivingflow rate and total volume information via an input signal from anexternal control system.

FIGS. 5 and 6 depict another embodiment similar to that depicted inFIGS. 1 and 2. As shown in FIG. 5, the embodiment includes a flowcircuit 2 having a bypass loop and an outlet flow branch. However, theembodiment of FIGS. 5 and 6 further includes secondary exhaust orifice16. The secondary exhaust orifice 16 may be in fluid communication withthe outlet branch valve 12 b and fluid exhaust channel 15. Preferably,fluid passed through outlet branch valve 12 b, then through secondaryexhaust orifice 16 before passing into exhaust channel 15 and outcircuit fluid outlet 4. The secondary exhaust orifice 16 may be anadjustable valve, such as a needle valve. Alternately, secondary exhaustorifice 16 may be replaced with an orifice size selector, such asorifice size selector 30 of FIG. 3.

The secondary exhaust orifice, which is preferably adjustable, providesadditional self priming capability for higher viscosity fluids(typically greater than 10 cP), as well as for applications where thedosing pump must draw fluid from a source or flow fluid to destinationlocated at a relatively large vertical height differential from thedosing pump itself (i.e. vertical head). Without the secondary exhaustorifice 16, for high viscosity fluid and/or pumping against a largevertical head, there is potential for the pump to fail to createsufficient pressure to overcome the flow losses due to viscous effects,vertical head loss, and flow restriction of fluid attempting to passthrough orifice 11 b, resulting in a failure of the dosing pump toprime. Enlargement of orifice 11 b reduces flow losses through theorifice, permitting the system to create fluid flow through the outletbranch, allowing the dosing pump to prime. However, enlargement of theorifice 11 b sacrifices control of the fluid output once the pump isprimed and system is sufficiently filled with fluid.

Accordingly, the addition of the secondary exhaust orifice 16 enablesorifice 11 b to be differently sized, including relatively large sized,in order to reduce the flow losses of fluid passing through orifice 11b, thereby allowing the dosing pump to initially prime, whilemaintaining control over the fluid flow rate through the outlet branch.The addition of secondary exhaust orifice 11 b compensates for the lossof flow control resulting from the larger size of orifice 11 b, enablingthe dosing pump system to maintain the intended flow output that wouldbe achieved with a smaller size of orifice 11 b alone.

In operation, the combination of orifice 11 b and secondary outletorifice 16 provide additional self priming capacity in the followingmanner. When the pump 1 is energized and prior to the flow circuit beingsufficiently filled with the fluid to be pumped, the relatively higherrestriction created by the flow orifice 11 a and bypass loop valve 12 ain the bypass loop forces air to flow through the outlet flow branchwith the relatively lower flow restriction created by the flow orifice11 b and the secondary exhaust orifice 16. As the air is forced throughthe outlet branch of the flow circuit, increased suction is created atthe inlet 3 and the liquid being pumped is drawn into the pump 1,priming the pump. Once the flow circuit has become sufficiently filledwith fluid, the higher viscosity of the fluid in comparison to aircreates relatively large flow rate within the bypass loop and creates alower flow rate within the outlet flow branch.

Another feature of the embodiment utilizing the preferably adjustable,secondary exhaust orifice 16 is the ability to adjust the restriction atthe dosing pump outlet, allowing for an increased adjustment of the flowrate over a range of fluid viscosities. The embodiment of FIGS. 5 and 6may, just as with the embodiment described with relation to FIGS. 1 and2, further include a control system as described above. Similarly, theembodiment of FIGS. 5 and 6 may further include the orifice sizeselector 30, described above with relation to FIG. 3.

While, as discussed above, the controller of the pump system may controlthe operation of the pump through adjustment of the pump motor emf, itis recognized that it in many applications, it may be desirable toactually sense and determine the fluid flow in the input flow channel 5(see FIGS. 1 and 5). A further embodiment of the present inventionincludes an additional flow rate sensor. In the dosing pump systemdescribed above, the flow rate may be monitored utilizing a traditionalflow sensor even where the pump output is at a microdosing level. Anexample of a suitable traditional flow senor is the FT-110 Seriesturbine senor available from Gems Sensors and Controls located at OneCowels Road, Plainville, Conn. 06062.

As discussed above, the combination of the bypass loop and outlet branchallows the pump to operate at a relatively high velocity, regardless ofthe desired output of the pump system, such that a relatively high fluidflow is achieved in the bypass loop while a lower flow, and particularlya microdose flow, is achieved in the outlet branch. Referring now toFIGS. 1 and 4, for example, sensing the motor emf 43 of the pump motorwill provide feedback information regarding the operation of the pump 1,and hence the volume of fluid dispensed through the outlet port 4. Inthe further embodiment, it is preferable that a traditional flow sensor(not shown) is placed in the input flow channel 5 between junction 14and pump input 6 to sense the fluid flow though input flow channel 5.Due to the configuration of the flow circuit 2, when the pump system isoperated to provide a microdose output flow at outlet port 4, arelatively high flow rate, greater than microdosing levels, develops inthe bypass loop, and particularly through input flow channel 5. Becausethe flow rate is higher, the traditional flow rate sensor, despite arelatively low sensitivity, is capable of accurately sensing the flowrate of fluid in the input flow channel 5. The sensor may then outputinformation respecting the flow rate to a controller of the dosing pumpsystem.

Thus, in a practical application, for a given fluid, having knownproperties (such as a known viscosity), and for a desired output flowrate, the proportionality between the desired output flow and the bypassloop flow is known. The output flow of the dosing pump system may becalculated by the controller by utilizing the data output by atraditional flow sensor measuring the flow of fluid passing throughinput flow channel 5. The controller may also vary the voltage appliedto the pump to adjust the output flow rate and thereby achieve thedesired output flow.

Although the present invention has been described in terms of thepreferred embodiments, it is to be understood that such disclosure isnot intended to be limiting. Various alterations and modifications willbe readily apparent to those of skill in the art. Accordingly, it isintended that the appended claims be interpreted as covering allalterations and modifications as fall within the spirit and scope of theinvention.

What is claimed is:
 1. A pump system comprising: a fluid pump having anpump input and a pump output in fluid communication with a fluid flowcircuit wherein said flow circuit comprises: an inlet port; an inletflow channel providing fluid communication from the inlet port to thepump input; an output flow channel in fluid communication with the pumpoutput; a bypass flow orifice; a bypass loop valve, wherein the outputflow channel provides a fluid path from the pump output to the bypassloop valve and the bypass loop valve is disposed downstream from thebypass flow orifice; a return channel disposed downstream from thebypass loop valve, wherein the return channel is connected to the inletflow channel and forms a fluid pathway between the bypass loop valve andthe inlet flow channel; an outlet branch connected to the output flowchannel upstream from the bypass flow orifice; an outlet flow orifice;an outlet branch valve, wherein the outlet branch provides a fluidpathway from the pump output to the outlet branch valve and the outletbranch valve is disposed downstream from the outlet flow orifice; and anoutlet port disposed downstream from the outlet branch valve.
 2. Thepump system of claim 1 wherein, the outlet flow orifice is connected tothe outlet branch valve.
 3. The pump system of claim 1 wherein, thebypass flow orifice is connected to the bypass loop valve.
 4. The pumpsystem of claim 1 further comprising: an exhaust channel disposedbetween the outlet branch valve and the outlet port so as to form afluid pathway from the outlet branch valve to the outlet port; whereinthere exists no fluid pathway between the exhaust channel and the pumpinput.
 5. The pump system of claim 1 comprising: only a single fluidpathway between the pump output and the inlet flow channel.
 6. The pumpsystem of claim 5 wherein, the single fluid pathway between the pumpoutput and the inlet flow channel consist of: the output flow channel;the bypass flow orifice being disposed downstream from the pump output;the bypass loop valve being disposed downstream from the bypass floworifice; and the return channel being disposed downstream from thebypass loop valve and connecting the bypass loop valve to the inlet flowchannel.
 7. The pump system of claim 1 wherein, the return channelincludes only a single inlet at the bypass loop valve and a singleoutlet that is connected to the inlet flow channel.
 8. The pump systemof claim 1 wherein, the exhaust channel includes a secondary exhaustorifice.
 9. The pump system of claim 8 wherein, the secondary exhaustorifice comprises an adjustable valve.
 10. The pump system of claim 1wherein, the output flow channel, bypass flow orifice, bypass loopvalve, outlet branch, outlet flow orifice, outlet branch valve, and afirst portion of the inlet flow channel are formed in a first manifoldbody; the return channel, exhaust channel, and a second portion of theinlet flow channel are formed in a second manifold body; and wherein thefirst manifold body and second manifold body are connected such that thefirst portion of the inlet flow channel and the second portion of theinlet flow channel align, the return channel and the bypass loop valvealign, and the exhaust channel and outlet branch valve align.
 11. Thepump system of claim 1 wherein the bypass loop orifice and outlet floworifice are differently sized.
 12. The pump system of claim 11 whereinthe outlet flow orifice is larger than the bypass loop orifice.
 13. Thepump system of claim 1 wherein fluid is allowed to flow into the inletflow channel only from the inlet port and from the return channel andwherein all fluid flowing through the return channel flows first throughthe bypass loop orifice and then through the bypass loop valve.
 14. Thepump system of claim 1 wherein the bypass loop valve and the outletbranch valve are each check valves.
 15. The pump system of claim 14wherein the bypass loop valve has a cracking pressure that is greaterthan a cracking pressure of the outlet branch valve.
 16. The pump systemof claim 1 further comprising a fluid flow sensor adapted to sense thefluid flow within the inlet flow channel.
 17. The pump system of claim16 wherein the fluid flow sensor is positioned so as to sense the fluidflow that occurs in the inlet flow channel between the pump input andthe connection point of the return channel and the inlet flow channel.18. A pump system consisting of: a fluid pump having a pump input and apump output; an inlet flow channel connected to the pump input; anoutput flow channel connected to the pump output; a bypass loop valvehaving a bypass flow orifice in fluid communication with the output flowchannel such that the bypass flow orifice is disposed between the pumpoutput and the bypass loop valve; a return channel connected only to thebypass loop valve and the inlet flow channel and forming a single fluidpathway therebetween; an outlet branch connected to the output flowchannel wherein the connection location of the outlet branch the outputflow channel is between the pump output and the bypass flow orifice; anoutlet branch valve having an outlet branch orifice in fluidcommunication with the outlet branch such that the outlet branch orificeis disposed between the pump output and the outlet branch valve.
 19. Thepump system of claim 14 wherein the bypass loop valve and the outletbranch valve are each check valves.